Appending points to PCD and Out-of-core Octree modification to use append

The PCD writer now writes the width and number of points using 10 digits, so the header part of the PCD file is fixed.
There is a new call to append data to a PCD file.
The out-of-core octree has a specialization that is able to append data, instead of creating new point clouds and compressing them to disk.